An epidemiologic case-control study is proposed to determine if cholecystectomy is a risk factor for right-side colon cancer, left-side colon cancer, or rectal cancer. The study, which will be conducted at the Illinois Cancer Council, is designed to allow investigation of this relationship among males, females, and age-specific subgroups and by duration of exposure since cholecystectomy. Each of the three case groups will be compared to a single control series consisting of the spouses of the identified patients. Comparisons will be made of male cases with the spouses of the female cases and female cases with the spouses of the male cases. The gastrointestinal surgical history will be ascertained for all study subjects so that the presence or absence of a history of cholecystectomy can be noted. Cholecystectomy history will be obtained through telephone interviews and subsequently validated from operative and pathology reports at time of this surgery. Cholecystectomy history for the large bowel cancer patients will also be abstracted from hospital records at time of cancer diagnosis and attempts will be made to confirm the status of the gallblader through operative reports, oral or ultrasonic cholecystography and physical examinations. If the results of this investigation are positive, a larger study involving multiple centers is sugested to investigate the effects of gallbladder diesase, with and without cholecystectomy, on the risk for subsite-specific large bowel cancer. In addition, a clinical cross-sectional study involving large bowel cancer patients and controls, with and without cholecystectomy, might be justified. Such a study would include assays of fecal mutagens, fecal bile acid and cholesterol metabolites and intestinal bacteria, as well as mutagenic testing of subsite-specific large bowel epithelium. The relationship between biliary metabolism and large bowel cancer is unclear, and therefore the results from the current and potential, subsequent investigations may increase the understanding of this relationship. Thus, knowledge of the etiology of large bowel cancer may be increased.